Man moves 30,000 packages in 4 hours

Heilbronn, Germany--Each day shortly before 4 p.m., Hans Dieter Kupfer grabs a cup of coffee and climbs the ladder to his sound-proof perch atop 2,350 meters of conveyor lines. The Plexiglas control room, part of DPD's (Deutscher Paket Dienst GmbH & Co.) newest parcel distribution center, affords an unobstructed, 360-degree view of the facility's entire package-handling operation.

During the next four hours, however, Kupfer will rely on his computer screen for the big picture: Status of the system's 392 variable-frequency drives, package tracking, and speed of the different sections of steel conveyor belt. Such data, taken as a whole, helps him push 30,000 packages out the door and onto the appropriate trucks every afternoon.

Built by Hermann Schmidt Maschinenfabrik (Lünen-Lippoltshausen, Germany) for DPD, the Heilbronn facility is the latest and most technically advanced of the company's 45 fully automated parcel distribution centers installed since 1990.

"Reunification," says Plant Manager Peter Schönleber, "created an increase in commerce between East and West. The new depots were constructed to meet that demand." They also ensure 24-hour delivery throughout Europe.

A series of IR sensors, motors, and gearboxes--networked to the operating software via Mitsubishi PLCs and the company's Melsec Net fieldbus--run the system. On his screen in the control room, Kupfer follows a parcel from the receiving station to the delivery vehicle that carries it to its final destination.

Let's join him.

Parcel collection. One of 15 telescoping conveyors carries the package to the receiving station where it is assigned bar code labels for routing and identification. An Omnix^TM IR scanner, supplied by Accu-sort Systems Inc. (Telford, PA) and capable of 3-m/sec scan speeds, inputs the destination code/client information while a scale, integrated into the conveyor itself, records parcel weight.

Helical worm gearmotors, Type GSS05-2M made by Lenze GmbH & Co. KG (Hameln, Germany), drive the telescoping conveyors. To facilitate servicing, a shrink-disc compression coupling joins the conveyor shaft and gearbox.

Depending on which telescoping conveyor the package loads onto, it then passes to one of two collection conveyors. Short sections of steel belt, each section driven by a Lenze bevel gearmotor with integral brake and force ventilation, make up the collection conveyors. In-house software controls the variable-frequency drives and therefore the parcel stream.

In addition, regulating the speed of the collection conveyors' individual sections allows the two lines to merge into one, increasing flow capacity while maintaining a minimum distance of 20 cm between packages. Infrared sensors monitor package speed, while forced ventilation cools the motors at low speed.

Parcel sorting. Beyond the merge, an IR scanner reads the bar code once more. Information from the routing label activates a helical inline gearbox and Type 9200 servocontroller, both from Lenze. The drive, in turn, twists three small turntables with built-in rollers. The turntables direct the package to either sorter line A or Sorter Line B. There is no interruption in parcel flow as a 60-degree twist of the turntable takes just 200 msec.

The package then enters Sorter Line A or B, depending on final destination. Angled rollers orient it to the conveyor's inner wall--a series of vertical, moving steel belts--to minimize impact from one of 52 hinged diverters built into the wall. The diverters kick the parcel--which may weigh as much as 50 kg--towards its respective delivery vehicle much like a flipper knocks a pinball onto the game's playing field.

"Diverter reaction time," Schönleber points out, "is 250 to 300 milliseconds." To meet the high dynamics and low backlash requirements of the application, each diverter employs a Lenze helical gearbox operated by a Lenze Series 9200 controller. The result, Schönleber says, is a "more robust and much faster system than conventional tilt mechanisms or position controllers."

How long does it take our package to make its journey from receiving station to final destination conveyor? A mere 2.5 minutes. As the last truck departs DPD's Heilbronn depot, Kupfer descends from his control room, satisfied that 30,000 packages are on route to points throughout Europe. Not a bad day's work for one man--even if it was only four hours.